Daikin RXYQ96PYDN Service Manual page 484

SiUS34-801A_b
[Check 12] Check for shortage of refrigerant.
In case of VRV Systems, the only way to judge as the shortage of refrigerant is with operating
conditions due to the relationship to pressure control and electronic expansion valve control.
As information for making a judgment, refer to information provided below.
Diagnosis of shortage of refrigerant
1. The superheated degree of suction gas rises. Consequently, the compressor discharge gas
2. The superheated degree of suction gas rises. Consequently, the electronic expansion valve
3. Low pressure drops to cause the unit not to demonstrate cooling capacity (heating capacity).
Troubleshooting
temperature becomes higher.
opens.
Cooling
The opening degree of the indoor unit
motorized valve becomes larger.
High pressure
Low pressure
LP rises as the opening
degree of the indoor unit
motorized valve becomes
larger. Frequency slightly
increases under the
capacity control.
Frequency
Heating
The opening degree of the outdoor unit motorized valve becomes larger.
High pressure
Low pressure
Frequency
To maintain LP, frequency
drops due to the capacity
control.
Proper quantity
Troubleshooting (OP: Unified ON/OFF Controller)
Either of the motorized valves
becomes fully open.
Frequency comes to the minimum level.
HP drops with decrease
(LP is maintained
in compressor capacity.
at a constant level.)
To maintain LP,
frequency drops
due to the
capacity control.
The outdoor unit motorized valve fully opens and frequency increases.
Discharge pipe or LP drooping control
(HP is maintained
at a constant level.)
Frequency drops
due to the drooping
control.
(Degree of refrigerant shortage)
Fan control is activated for HP
protection under cooling control
at low outdoor temperature,
i.e., the fan is hunting at HP.
If frequency comes to the
minimum level, LP
cannot be maintained.
Frequency comes to
the minimum level.
Higher degree of shortage
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